The electric generation efficiency of fuel cells is high, and its environmental load is also low. Since solid polymer type fuel cells have a particularly high power density and a low operation temperature, miniaturization and cost reduction are easy, as compared to other fuel cells. Accordingly, the solid polymer type fuel cells are expected to be widely used for transporters such as automobiles, dispersion electric generation systems and cogeneration systems for houses.
In general, solid polymer type fuel cells are provided with a catalyst layer containing a metal catalyst and a sol)id polymer electrolyte resin (ion exchange resin) on both surfaces of the solid polymer electrolyte membranes respectively, and the outside of the catalyst layer is provided with a membrane/electrode assembly having a gas diffusion layer formed by using carbon paper or carbon cloth. Further, the outside of the gas diffusion layer is provided with an electrically conductive separator wherein a gas flow path is formed on its surface. The separator has a role to conduct current from the gas diffusion layer having a function to let fuel gas, oxidizing gas, etc. pass through and a function of a current collector to the outside portion of the solid polymer type fuel cell and a role to take out electric energy.
In a process for producing the fuel cells, a carrier film is used for forming or transporting a layer- or membrane-form member for fuel cells, such as a catalyst layer or a solid polymer electrolyte membrane. For example, a carrier film is coated with a solution containing a carbon carrying a metal catalyst and an ion exchange resin as the main solid component, followed by drying to form a catalyst layer, or a carrier film is coated with a solution containing an ion exchange resin as the main solid component, followed by drying to form a solid polymer electrolyte membrane.
The carrier film used for such applications is generally a polyethylene terephthalate (PET) film, a release agent-coated PET film or a fluororesin film.
However, among such films, the releasability of the PET film is poor. Further, in the case of the release agent-coated PET film, at a time of forming a component for fuel cells, the release agent transfers to deteriorate properties of the component for fuel cells. Further, although the fluororesin film has a good releasability, the fluororesin film is soft and handling property is poor. In order to solve such problems, it has been proposed to employ a laminated film wherein a fluororesin film and a film having a high rigidity are laminated (Patent Document 1).
Patent Document 1: JP-A-2003-285396